Soil Microbial and Ecological Investigations in the Antarctic Interior'

Soil Microbial and Ecological Investigations in the Antarctic Interior' Roy E. CAMERON, ROGER B. HANSON,

GEORGE H. LACY; and FRANK A. MORELLI Bioscience Section Jet Propulsion Laboratory California Institute of Technology In November–December 1969, 10 soil samples were collected aseptically from the surface to the depth of permafrost at 5 sites on a traverse west of Coalsack Bluff (approximately 84°15'S. 162°E.). Another 14 samples were collected from 5 sites on a traverse north of the Bluff. During the latter traverse, a camp site was established for one week just below the west end of "Coalsack Bluff West," and environmental measurements were made continually or every 3 hours for soil and/or microclimatic characteristics. Air sampling for microflora was also undertaken on 4 sides of the camp site. Soil properties were

'This paper presents the results of one phase of research carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract NAS 7-100, sponsored by the National Aeronautics and Space Administration. Logistic support and facilities for the investigations in Antarctica and additional laboratory support at JPL were provided under contract CO-585-000-00 with the National Science Foundation.

determined by methods used with desert soils and other geological materials from harsh environments. Abundances of various physiological groups of microorganisms were determined on standard media and by techniques used previously on antarctic soils containing few microorganisms (Benoit and Hall, 1970; Cameron, 1969). The soils were generally typical of the antarctic cold desert and similiar in many respects to other extremely and soils (Cameron, 1969). However, acid pH values, 5.2 and 5.3, and the reddish color of profile 725-726 indicated a tropical relict soil. Soils obtained on a traverse of the Bluff area were generally better developed and older, features characteristic of more mature dry-valley soils (Tedrow and Ugolini, 1966). Although the cation-exchange capacities (2-3 meq/100 g) and buffer capacities (1.5-7.5 meq/100 g) were relatively low, there were noticeable water-soluble amounts of predominately gypsic and natric salts. Nearly all samples were high in NO 3 – , indicating the aridity of the area. Organic C, except for nos. 742 and 749, was low (0.02-0.05 wt. %) and similar to that of other cold desert soils. However, the organic (Kjeldahl) N was quite high for such barren sites-0.3-0.4 wt. %, and the extremely narrow C: N (2-0.1) indicated either highly decomposed colloidal or microbial organic matter, or relict carbon such as coal (Horowitz et al., 1969). Our soil samples were obtained from a highly fossiliferous area containing coal and other carbonaceous sediments. Carbon particles were impacted on all of our air-sample filters. At the sites on the Bluff (725-726 and 731), es-

Table 1. Abundance of microorganisms in antarctic soils (per gram of soil) Sam- Sample ple depth No. (cm)

Aerobic bacteria

Micro- Lactose Nitrate Nitrogen Yeasts aerophiles fer- reducers fixers menters

725 Surf. 2 9 726 2—.-. 10 0

0 0 0 0 0 0

0 0

731 Surf.2